Recently there have been developed various air bag devices for ensuring the safety of a passenger upon occurrence of an accident of traffic means, especially an automobile, and the usefulness thereof has been recognized. Consequently, air bag devices have come to be attached in a very high rate to automobiles. Such air bag devices are each made up of a sensor for sensing a state of rapid deceleration upon, for example, collision of an automobile equipped with the air bag device, an inflator which generates a high pressure gas upon receipt of a signal from the sensor, an air bag adapted to swell and develop under the high-pressure gas generated from the inflator, and a diagnosing circuit which determines whether the air bag device functions normally or not.
As examples of materials employable for the airbag there are various materials, including a coated fabric comprising a high tenacity filament fabric such as polyamide and a heat-resistant elastomer such as chloroprene coated on the fabric. By applying the heat-resistant elastomer to the surface of the fabric it is intended to improve the performance which with the polyamide fiber fabric alone is deficient, such as heat resistance, flame retardance and air shieldability. This coating process is useful also for the prevention of stitch dislocation and fray of the fabric.
However, the fabric becomes hard when coated and hence becomes difficult to be folded compactly, thus giving rise to a problem in point of stowability of the air bag. Moreover, for satisfying all of high heat resistance, flame retardancy and air shieldability, it is necessary that the amount of the heat-resistant elastomer applied per unit area of the fabric be 50 g/m2 or more, thus giving rise to the problem that the weight of the air bag increases.
In an effort to solve such problems, a base fabric for an air bag with a reduced amount of the heat-resistant elastomer applied thereto is now under study. For example, in Japanese Patent No. 2853936 there is disclosed an air bag wherein an elastomer resin is localized at a film thickness ratio of 3.0 or more in a fabric stitch portion relative to 1.0 of a weaving yarn portion which constitutes a fabric. In this air bag, although the stowability thereof is improved, the adhesion between the resin coating and the fabric cannot be considered sufficient. Further, in the case where the amount of the elastomer applied is as small as 20 g/m2 or less, it is difficult to satisfy the flame retardancy based on the resin coating, in such a localized state of the resin.
In JP 2004-124321A there is disclosed a base fabric for an air bag wherein at least one surface of the fabric is coated with resin and filaments in at least a part of the fabric is enclosed with the resin, while filaments in at least another part of the fabric is not enclosed with the resin. According to this fabric, although the stowability of the air bag and the adhesion between the resin coating and the fabric are improved, it cannot help being considered that the fabric is insufficient in point of flame retardancy based on the resin coating.